Dumas Method Chem Lab 1 PDF

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Experiment 1: Dumas Method Purpose The purpose of this experiment was to determine the experimental molar mass of an unknown organic solvent and use the Dumas Method to identify it from a list of four possibilities.

Introduction There are three simple gas laws that each present an effect a certain variable will have on the volume of a gas when other variables are held constant.2 These three laws, presented by Boyle, Charles, and Avogadro, have been combined to form one ideal gas law which includes all four variables: volume (V), pressure (P), number of moles of gas (n), and temperature (T). 1 Ideal Gas Law: PV = nRT R represents the ideal gas constant, which is equal to 8.31451 J/mol K. 1 The ideal gas law is used in the Dumas Method to determine the molar mass of an unknown compound. Developed by Jean-Baptiste Dumas in the 19th century, the Dumas Method is a method to determine the molar mass of a gas using a modified version of the ideal gas law.3 Dumas: M = (nRT)/PV M in this equation represents the molar mass of the gas being used. By finding the volume, pressure, and temperature of a substance in its gas phase, the ideal gas law can be used to find the number of moles in the given substance. The Dumas Method can then be used to calculate the molar mass of the compound, allowing the compound to be identified.

ou can then use the ideal gas law to calculate the number of moles of the substance. Finally, you can use the

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number of moles of the gas to calculate molar mass. This process can be done using the ideal gas law which is pressure and volume is proportionate to number of moles, the universal gas constant and temperature. ou can then use the ideal gas law to calculate the number of moles of the substance. Finally, you can use the number of moles of the gas to

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calculate molar mass. This process can be done using the ideal gas law which is pressure and volume is proportionate to number of moles, the universal gas constant and temperature. You can then use the ideal gas law to calculate the number of moles of the substance. Finally, you can use the number of moles of the gas to calculate molar mass. This process can be done using

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the ideal gas law which is pressure and volume is proportionate to number of moles, the universal gas constant and temperature. You can then use the ideal gas law to calculate the number of moles of the substance. Finally, you can use the number of moles of the gas to calculate molar mass. This process can be done using the ideal gas law which is pressure and volume is

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proportionate to number of moles, the universal gas constant and tem Procedure -

Determine mass of Erlenmeyer flasks, aluminum foil and rubber bands

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Add unknown organic solvent

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Heat Erlenmeyer flasks containing solvent in boiling water baths 

Ensure magnetic stir stick is in bottom of water bath beakers

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Measure temperature of boiling water baths after solvent has vaporized

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Using tongs, remove flasks from heat and allow vapor to condense for 10-15 min

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Determine mass of Erlenmeyer flasks, aluminum foil, rubber bands and condensed vapor

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Dispose of organic solvent safely in organic waste bottle

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Determine overall volume of Erlenmeyer flasks

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Clean up

Observations When determining the mass of the Erlenmeyer flask, aluminum foil and rubber bands, the values all varied slightly but were relatively similar. After adding the clear, colourless organic solvent to the flasks and placing them in the warm water baths, condensation began to form on the inside of the Erlenmeyer flasks. As time went on and the temperature of the hot plate was brought to 350 ° C, the water in the water baths began to bubble and eventually boil, producing lots of steam. The temperature was then turned to between 200 ° C and 150 ° C, causing the large bubbles to gradually reduce to a low boil. Once there was no visible solvent left in the flasks, the temperature of each water bath was measured, each beaker of water being approximately 373 K. The Erlenmeyer flasks were then removed from the water baths, and after having 10 minutes to cool there was no visible condensation or liquid. When determining the mass of the Erlenmeyer flask, aluminum foil, rubber bands and condensed vapor, the overall mass of each trial varied significantly, however; the mass of the condensed vapor for all three trials seemed to be similar.

Questions 1. Calculate the mean (molar mass) and standard error of the sample for your results. Mean: (55.2 g/mol + 53.7 g/mol + 57.8 g/mol) Standard Deviation of the Mean (SDM): 1.69350

÷ 3 = 55.6 g/mol

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Standard Error:

SDM ÷ √ N=1.69350 ÷ √ 3=0.978

2. Based on the molar mass you determined, identify the particular organic compound you used from the list of options presented on the datasheet. Based on the molar mass of the data, the organic compound #2 is determined to be acetone. With its molar mass of 58.1 g/mol, acetone has the closest molar mass to the calculated molar mass of 55.6 g/mol, their difference being 2.5 g/mol.

3. Give three sources of experimental error that may have caused your answer to be incorrect and explain how your error would have changed your final conclusion. 1. Irregular boiling of the organic liquid: The hot plates would not keep the boiling water baths at a steady temperature, so the organic liquid in the baths was constantly going from hot to cold instead of gently boiling at a steady rate as outlined in the Lab Manual.1 This made it difficult to tell when the organic liquid had fully evaporated in the Erlenmeyer flask, possibly skewing the data when testing the mass of the condensed vapour. 2. Precision of the measurements of the overall volume of the Erlenmeyer flasks: It was difficult to pour a full Erlenmeyer flask of water into the graduated cylinder without spilling some over the lip of the flask. Because of this, it would be very difficult to find the exact volume of the Erlenmeyer flask, therefore throwing off the Vapour Data calculations in this lab. 3. Possibility of extra liquid trapped under the seal on the Erlenmeyer flask: If there was extra condensation under the seal when the flasks were weighed, this would have resulted in an overestimate of the overall mass of the organic compound.

Experiment 1 data sheet. This sheet is available for download from the onQ web site.

Na me :El i z a be t hVa nHor ne

Pa r t ne r :Ta ma r aSma l l woo d

St u de ntNo:2 0143 365

St u de ntNo:2 0000 793

La bSe c t i on:015

Be nc h#( onc omp ut e rs c r e e n) :1 6

DATA SHEET

Sa mp l enumb e rf r omt hes t oc k bo t t l ey ouus e d.

Ma s s flas k +2. 5”x 2. 5”Alf oi l = +r ubbe rband

2 Tr i a l1*

Tr i a l2

Tr i a l3

un i t s

9 4. 22

90 . 56

96. 73

g

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Ma s s ofabo v e+c ompound af t e rhe at i n g Ma s s c onde n s e dv apour VapourDa t a Vol u me Te mp e r a t u r e Pr e s s ur e Mo l a rMa s s Me a nofMo l a rma s s e s St a nda r dEr r oroft he me a nmo l a rma s s

= m=

V= T= P= M=

M´

9 4. 51

90 . 83

97. 03

0. 29

0. 27

0. 30

159

152

157

373 . 6

373. 2

373. 4

102. 6

1 02. 6

10 2. 6

55 . 2

53. 7

57. 8

( 55. 2g/ mol+53. 7g/ mol+57. 8g/ mol )÷

g g

mL K kPa 1 gmol

3=55. 6g/ mol

σ x

1.69350÷ √ 3=0.978

References [Each reference listed here should have a number that corresponds to the superscripted number in the body of the report where this reference is pertinent.] 1. Queen’s University. (2019). Queen’s Chemistry: First Year Laboratory Manual Chemistry 112 (2019th -2020th ed.). 2. Petrucci, & Herring. (2017). General Chemistry: Principles and Modern Applications (11th ed.). Pearson Canada. 3. 11B: The Dumas Method (Experiment). (1983). CRC Handbook of Chemistry and Physics (64th ed.). Retrieved from https://chem.libretexts.org/Ancillary_Materials/Laboratory_Experiments/Wet_Lab_Experiments /General_Chemistry_Labs/Online_Chemistry_Lab_Manual/Chem_11_Experiments/11B %3A_The_Dumas_Method_(Experiment)...